1. Field of the Invention
This invention relates to novel silicate-containing oil recovery surfactant compositions and methods of using the same in steam recovery systems to enhance the recovery oil from subterranean formations. More particularly, these compositions comprise certain anionic surfactants, in combination with hydrotropes and alkali metal silicates, and methods comprising injecting these compositions with steam into oil-bearing formations to greatly increase heavy oil recovery as compared with the use of surfactant-hydrotrope compositions alone.
This invention also relates to the method of recovering oil with steam wherein a combination of said surfactants and said silicates, without the hydrotrope, are employed to enhance the oil recovery.
2. Description of the Prior Art
The use of secondary and tertiary oil recovery techniques, with or without the addition of various reagents such as surfactants, water thickeners and the like to recover crude oil left behind in formations after the "primary" oil has been withdrawn is well established in the art. These displacement methods have been improved by the addition of surfactant compositions in both secondary and tertiary processes, for example where a formation has already been waterflooded at least once.
Representative of these prior art compositions and methods are those taught in U.S. Pat. Nos. 3,348,611 to Reisburg; 3,885,626 to Gale et al; 3,901,317 to Plummer et al; 3,994,342 to Healy et al; and 4,295,980 to Motz, all of which teach aqueous flooding techniques with at least one surfactant, and in some cases, with viscosity modifiers, co-surfactants or the like. In a unrelated field, U.S. Pat. No. 3,501,409 teaches a liquid washing detergent composition comprising said detergent in combination with a hydrotrope. Similarly, U.S. Pat. No. 4,165,294 teaches a commercial photoresist stripping solution comprising an alkylaruyl sulfonic acid and a hydrotope aromatic sulfonic acid. This composition, used to remove organic coatings from inorganic substrates, is further characterized in requiring the presence of a solvent and also requiring that the composition must be phenol-free and halogen-free. Finally, U.S. Pat. No. 3,354,091 discloses a heavy-duty liquid detergent consisting essentially of a 5-component composition requiring the presence of an alkali metal anionic surfactant, a polyphosphate salt, a hydrotrope, carboxymethylcellulose, and hydrogenated castor oil. Optionally, small amounts of sodium silicate may, for undisclosed reasons, be added as long as it does not adversely affect the desired properties of the composition.
It is also known from U.S. Pat. Nos. 2,920,041; 3,805,893; 3,871,452; 3,871,453; 3,920,074; and 4,141,416 to employ alkali metal silicates as additives in secondary and tertiary oil recovery methods which use aqueous flooding techniques. Further, it is known more recently to combine these and other silicates with surfactants in the form of micellar solution of high or low molecular weight surfactants such as alkyl aryl sulfonates, or mixtures thereof, as shown in U.S. Pat. Nos. 4,011,908 and 4,037,659. However, in the case of these latter two patents, it will be noted that the mechanism whereby micellar solutions operate in aqueous systems in significantly different from those of steam recovery systems of the present invention, as described below.
In addition to the aforedescribed aqueous flooding techniques, the art has also employed steam for tertiary oil recovery, utilizing the effect of heat to obtain heavy oil from the formations in which it is found. See, for example, U.S. Pat. Nos. 3,357,487 and 3,994,345. However, the mechanism and effects of surfactants and modifiers under these high temperatures and diverse formation conditions remain unclear, and thus make it impossible to predict from a knowledge of the effects of aqueous surfactant systems which surfactants, if any, can advantageously be employed in these steam recovery conditions. This is even more true in the choice of any modifiers which might enhance the effectiveness of the surfactant.
It is, therefore, an object of this invention to provide a novel silicate-containing surfactant composition useful for enhancing steam recovery processes for tertiary recovery of heavy oil from subterranean formations.
It is a further object of this invention to provide an improved steam recovery process for enhanced oil recovery, utilizing the novel compositions provided herein.
Further objects and advantages of the compositions and methods of the present invention will become apparent in the course of the following detailed description thereof.